Dart

Encrypt a file to a PKCS7 encrypted message using multiple certificates from different users

See more Encryption Examples

Demonstrates how to encrypt a file to a PKCS7 encrypted message using multiple certificates from different users. Any one of the users can decrypt using his/her own certificate + private key.

Note: When doing public key encryption, it is the public key that is used to encrypt. The private key is required for decryption.

Dart

import 'package:chilkat/chilkat.dart';

void main() {
  // This example requires the Chilkat API to have been previously unlocked.
  // See Global Unlock Sample for sample code.

  final crypt = CkCrypt2();

  // Tell the crypt object to use 3 certificates.
  // Do this by calling AddEncryptCert for each certificate.

  // Load a digital certificate. 
  // We don't need the private key for encryption.
  // Only the public key is needed (which is included in a certificate).
  final cert1 = CkCert();
  cert1.loadFromFile('qa_data/user1/cert_user1.pem');
  // Assume success for the example, but make sure your application checks for success/failure...
  crypt.addEncryptCert(cert1);

  final cert2 = CkCert();
  cert2.loadFromFile('qa_data/user2/cert_user2.pem');
  crypt.addEncryptCert(cert2);

  final cert3 = CkCert();
  cert3.loadFromFile('qa_data/user3/cert_user3.pem');
  crypt.addEncryptCert(cert3);

  // Indicate that we want PKI encryption (i.e. public-key infrastructure)
  // to produce a CMS message (Cryptographic Message Syntax/PKCS7),
  // that is be created with RSAES-OAEP padding, SHA256, and AES-128 for the
  // bulk encryption.
  crypt.cryptAlgorithm = 'pki';
  crypt.pkcs7CryptAlg = 'aes';
  crypt.keyLength = 128;
  crypt.oaepHash = 'sha256';
  crypt.oaepPadding = true;

  // Load the file to be encrypted...
  final fileData = CkBinData();
  fileData.loadFile('qa_data/jpg/penguins.jpg');
  // Your app should check for success/failure..

  // Encrypt the data.  The contents of the fileData object are replaced with the PKCS7 encrypted message.
  try {
    crypt.encryptBd(fileData);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Save the PKCS7 encrypted message to a file..
  fileData.writeFile('qa_output/pkcs7_encrypted.p7');

  // Now indicate that the PKCS7 output is to be returned in the base64 encoding.
  crypt.encodingMode = 'base64';

  print('OK.');
}